Mountain Lady’s Slipper

Rare Plant Profile – Mountain Lady’s Slipper (Cypripedium montanum Dougl. ex Lindl.)

Mountain lady’s slipper (Cypripedium montanum) is a perennial herb in the Orchidaceae Family[1]. Its leafy stems emerge from underground rhizomes to grow 20-50 cm tall. Leaves are alternate, egg-shaped to broadly lance-shaped with many parallel veins. Two or three sweet-scented flowers are found near the end of the stem. Flowers are white and purple, or purplish green in colour, with 3 lance-shaped sepals, 2 narrowly lance-shaped, twisted petals, spreading to the sides, with a broad, white-pouched lower lip petal that has an egg-shaped, purple-dotted, yellow lobe at the mouth of the pouch. Another similar species that also has a white-pouched lower lip is the sparrow’s-egg lady’s slipper (Cypripedium passerinum Richards.) but this more common species has much smaller flowers with flat petals and short, egg-shaped sepals. Small native bees pollinate the flowers by crawling into the pouch, transferring pollen as they do so[2].

In Canada, mountain lady’s slipper can be found in moist, open coniferous, deciduous, and mixedwood forests, and forest openings[3] in the montane regions of British Columbia, Alberta, and Saskatchewan[4]. Note that there is some uncertainty as to the natural origin of the Saskatchewan population found in the Cypress Hills[5]. The conservation status rank of mountain lady’s slipper is G4 (Apparently Secure) globally, N4N5 (Apparently Secure) nationally, and S2 (Imperiled) provincially[6]. In Alberta, this ranking is due to habitat loss, fire suppression, harvesting of wild plants, grazing pressures, disturbances due to construction and incidental loss due to the collection of other wild species[7]. Due to their small extent, populations of mountain lady’s slipper can be easily destroyed and rarely survive being transplanted[8].